1. Field of the Invention
The present invention relates to an organic electroluminescent (EL) light-emitting apparatus including a prism member, a polarizing member, and a phase member disposed at a light extraction side.
2. Description of the Related Art
In a self-light-emitting device (e.g., an organic EL device), light incident at an angle larger than a critical angle on an interface having a larger index difference, such as that between a substrate of the device and air, is totally reflected. Therefore, actually only approximately 20% of the total amount of emitted light can be extracted to the outside. To address this problem, a technique to increase the efficiency of light extraction by providing projections and depressions to a light-extraction surface of the device is proposed.
One technique to increase brightness in a known display apparatus is described in Japanese Patent Laid-Open No. 4-67016 and No. 6-308485. The technique causes light from a backlight source to efficiently converge to the front observation direction via a prism member having an optimal shape (e.g., triangular column, quadrangular pyramid) inserted in a path over which the light is guided to a liquid crystal display panel.
Japanese Patent Laid-Open No. 2005-55481 discloses an organic EL panel, which has a self-light-emitting light source. With the aim of sufficiently improving brightness, the organic EL panel is provided with a prism member.
Japanese Patent Laid-Open No. 2002-216947 discloses another organic EL panel, which has a self-light-emitting light source. With the aim of providing the organic EL display apparatus with bright display conditions with low power consumption, the organic EL panel is overlaid with a circular polarizer and a microlens sheet.
Japanese Patent No. 3,543,951 discloses another organic EL panel, which has a self-light-emitting light source. With the aim of providing an image display apparatus that can increase brightness observed from the front of a display screen without distorting a displayed image, the organic EL panel is overlaid with a prism sheet and a circular polarizing filter.
However, the above patent documents do not sufficiently study an application of a prism member to a light emitting apparatus that projects less glare of outside light. For an arrangement that has a prism member and a circular polarizer, the prism member contributes to an improvement in the efficiency of light extraction and the circular polarizer contributes to a reduction in reflection of outside light. However, the prism member affects the reflection of outside light and that property must be taken into account when reduction of glare is desired. Japanese Patent No. 3,543,951, which is mentioned above, discloses an arrangement that has a prism sheet and a circular polarizing filter, but does not describe the influence of the prism sheet on the reflection of outside light. It is necessary to consider the positions and the structures of components in an arrangement that has the prism member and the circular polarizer.